With ongoing growth of bandwidth requirements of users, fiber access is now a mainstream scheme in an access network, and a passive optical network is especially more competitive. Currently, in many passive optical network solutions, a WDM-PON (wavelength division multiplexing passive optical network) based on a wavelength division multiplexing (Wavelength Division Multiplexing, WDM) technology attracts much attention due to merits such as more enormous bandwidth capacity and information security similar to point-to-point communication.
In a WDM-PON system, transceiver modules of different ONUs (Optical Network Unit, optical network unit) need to communicate with a transceiver module corresponding to an OLT (Optical Line Terminal, optical line terminal) at the central office end by using different communication wavelengths. Therefore, the WDM-PON system requires light sources of different transceiver modules to transmit optical signals of different wavelengths.
To implement colorless light sources, an injection locked FP-LD (Fabry-Perot) laser diode based on external seed light injection or an RSOA (Reflective Semiconductor Optical Amplifier, reflective semiconductor optical amplifier) is proposed as a light source of the WDM-PON system in the industry.
Nevertheless, the injection locked laser solution based on external seed light injection requires one or two high-power flat wide-spectrum light sources as external seed light sources, and the costs are high. In addition, to make the communication wavelength vary between the ONUs, the spectrum of the wide-spectrum light source needs to be segmented, where the spectral segmentation brings a serious problem of power waste.